Hypothesis 1: Bone Injury

Based on the information provided by the physical exam, it seems likely the dog has 
fractured one or more bones.  The right tibia may be broken and possibly a fracture of the 
upper femur or pelvis on the left side.  Since the accident occurred three days ago, the 
dogÕs bones are attempting to heal.  The first step of healing is inflammation.  The 
periosteum of the bone is likely torn.  The soft tissue surrounding the bones and many of 
the nearby vessels were likely torn during the accident as well.  This explains the soft 
tissue swelling noted and the pain associated with the injuries.  A hematoma forms near 
the boney ends of the fracture and then clots, again supporting the swelling.  Due to the 
damaged vessels and the hematoma formation, sufficient blood does not reach the 
osteocytes at the fracture edges and they die.  Inflammatory mediators migrate into the 
area of damage, the vessels vasodilate, and edema results.  If more time is allowed to pass 
without veterinary intervention, the dog will eventually begin reparitive and remodeling 
changes in the bone.